You are building a system to generate unique usernames for employees based on their full names. The system must produce usernames that are consistent, concise, and duplicate-free.

You are given a list of strings names, where each string is an employee's full name in the format "<Given Name> <Middle Names...> <Family Name>". Your goal is to return a list of usernames corresponding to these names.

Username Requirements:

• Uniqueness: Each username must be unique within the returned list.
• Format: Usernames must contain only lowercase English letters and digits.
• Length: Each username must have a maximum length of 8 characters.